Surface Deformation is caused by which combination of factors?

• A. Weathering of the entire surface.
• B. Excess sand content in the mix or poor compaction.
• C. Corrugation (washing boarding), stopping or turning traffic, down grade braking, and poor mix design.
• D. Insufficient compaction.

Answer: (C)

Surface deformation happens when repeated traffic loading interacts with a pavement that can’t adequately resist the resulting stresses. Corrugation, or washboarding, is a rhythmic surface wave pattern created by wheel-path contact under cyclic loading. When vehicles brake on downgrades, or stop and turn, those transverse and longitudinal forces disturb the surface texture and promote ridges and valleys. If the mix design is poor, the asphalt binder and aggregate aren’t able to hold the structure together or recover after each load, so these disturbances deepen into permanent deformation. Weathering the entire surface is a gradual aging process and doesn’t explain the specific surface waviness and its enhancement by traffic actions. While too much sand in the mix or insufficient compaction can contribute to weaknesses, the combination of corrugation with braking, stopping, turning on grades, and a weak mix best explains surface deformation.